asterisk users - Aug 2005 - How to configure * for Net2phone using innomedia settings

Hello all:

I need help configuring * to register with Net2phone using the 
credentials provided with an Innomedia MTA 3328-2r fxs device. In using 
ethereal I see where the user agent string includes the MAC address of 
the device. Net2phone also is using MD5 authentication.

If the mac address is in the  user agent string does that prevent me 
from registering with 2 different Innomedia Accounts on the same * box?

Is there a way for asterisk send a variable user agent string depending 
on the account?